Novel cyanate ester compound, flame-retardant resin composition, and cured product thereof

ABSTRACT

A cyanate ester compound represented by the formula (1),  
                 
         wherein Ar 2  represents a phenylene group, a naphthylene group or a biphenylene group, Ar 1  represents a naphthylene group or a biphenylene group when Ar 2  is a phenylene group, or Ar 1  represents a phenylene group, a naphthylene group or a biphenylene group when Ar 2  is a naphthylene group or a biphenylene group, R x  represents all substituents of Ar 1  each R x  is the same or different and represents hydrogen, an alkyl group or an aryl group, R y  represents all substituents of Ar 2 , each R y  is the same or different and represents hydrogen, an alkyl group or an aryl group, and n is an integer of 1 to 50.

FIELD OF THE INVENTION

The present invention relates to a novel cyanate ester compound, athermosetting resin composition containing the above compound and acured product thereof. The cyanate ester compound of the presentinvention can provide a polymer material excellent in flame resistance,heat resistance and low dielectric characteristics by polymerizing thecyanate ester compound itself or copolymerizing the cyanate estercompound with another resin. Such a thermosetting resin composition canbe widely used for applications such as an electrical insulatingmaterial, a resin for a resist, a semiconductor-sealing resin, anadhesive for a printed wiring board, a matrix resin for a laminate or aprepreg used for electrical devices, a buildup laminate material, aresin for a fiber-reinforced plastic, a sealing resin for a liquidcrystal display panel, a resin for a color filter of liquid crystal, acoating composition, various coating agents and an adhesive.

PRIOR ARTS OF THE INVENTION

Cyanate ester resins generate a triazine ring by curing and have beenwidely used as raw materials for a variety of functional polymermaterials such as structural composite materials, adhesives, electricalinsulating materials or electrical and electric parts due to their highheat resistance and excellent electric characteristics. However, inrecent years, as higher performances are required in their applicationfields, physical properties required as a functional polymer materialbecome severer increasingly. As such physical properties, for example,there are required flame resistance, heat resistance, low dielectricconstant, low dielectric loss tangent, weather resistance, chemicalresistance, low moisture absorptivity, high fracture toughness, etc. Sofar, these required properties have not completely satisfied.

In a printed wiring board material field, for example, as acommunication frequency and a clock frequency are increasing, a materialhaving a low dielectric constant and a low dielectric loss tangentbecomes required. For this reason, cyanate resins excellent indielectric characteristics come to be used. In this case, it isnecessary to impart flame resistance in view of safety from fire andbromine compounds having high flame resistance are used. For example,brominated bisphenol A (JP-B-4-24370), a glycidyl ether of brominatedphenol novolak (JP-A-2-286723), brominated maleimides (JP-A-7-207022),halogen-containing monofunctional cyanates (JP-A-6-122763) and anadditive type bromine compound having no reactivity with a cyanate estercompound (JP-A-2000-95938) are known.

Such bromine compounds have high flame resistance, while corrosivebromine and hydrogen bromide are separated therefrom by thermaldecomposition. Therefore, materials which do not contain a bromine typeflame retardant are desired.

Then, phosphorus-containing compounds, nitrogen-containing compounds andsulfur-containing compounds have been studied as a flame retardantinstead of bromine. For example, triphenyl phosphate, resorcinolbis(diphenylphosphate), etc., are studied as a phosphorus compound whichis often incorporated into an epoxy resin. However, when such a compoundis incorporated in a large amount, heat resistance, moisture resistance,water absorptivity, etc., decrease in many cases.

For overcoming the above problem, a method in which a phosphoruscompound having a phenolic hydroxyl group is added to a cyanate compound(for example, JP-A-2003-128928, JP-A-2003-128753 and JP-A-2003-128784)is known. However, the phosphorus compounds also have a toxic problem.Furthermore, melamine, guanidine, etc., are used as a nitrogen compound.However, the nitrogen compound is insufficient in flame resistance whenit is used alone.

On the other hand, metal hydroxides such as aluminum hydroxide andmagnesium hydroxide are known as a flame retardant. However, there isapprehension that the incorporation of the metal hydroxide causes adecrease in dielectric characteristics, heat resistance, impactresistance or moldability. Further, when an inorganic filler such as aspherical fused silica is used in a large amount for decreasing acombustible component and securing flame retardancy, as is used for anepoxy resin, the melt viscosity of a molding material rises, adeterioration in moldability occurs, a decrease in adhesive strengthoccurs because of a decrease in wettability to a base material, or adeterioration in dielectric characteristics occurs, in some cases.

Further, antimony type flame retardants such as antimony trioxide, whichare widely used in combination with a brominated epoxy resin, have aproblem such as an apprehension of chronic toxicity since they are toxicsubstances. From the above viewpoints, thermosetting resins themselvesare desired to have higher flame retardancy than ever.

Moreover, a lot of attempts have been made for improving heatresistance, low dielectric constant, low dielectric loss tangent,weather resistance, chemical resistance, low absorption, high fractureresistance, moldability, adhesion, etc., in addition to flameretardancy. For example, JP-A-6-228308 discloses a method for producinga cured product excellent in thermal stability by combining amonocyanate with a dicyanate and JP-A-6-49238 discloses a method whichaims at a low dielectric constant and a low dielectric loss tangent bycombining a monofunctional cyanate ester compound with a polyfunctionalcyanate ester compound.

Further, JP-A-6-122763 discloses a method for producing alow-absorptive, flame-retardant cyanate ester curable resin compositionby incorporating a halogen-containing monofunctional cyanate ester inorder to achieve a low dielectric constant and a low dielectric losstangent. JP-A-6-122763 have a description about the cyanate ester in awide range. However, an aromatic monofunctional cyanate ester havingbromine as a functional group is essential for the maintenance of flameretardancy, so that JP-A-6-122763 does not succeeds in improving theflame retardancy with the cyanate ester resin alone.

Further, Japanese Kohyo No. 2002-531989 provides an aromatic cyanateester compound containing at least two rings each of which is bondedwith a group containing an unsaturated group. JP-A-63-250359 provides afluorine-containing dicyanate ester. JP-A-2002-206048 provides a methodfor attaining flame retardancy by using a phenol novolak type cyanateester. However, none of them teach a cured product formed of a cyanateester compound alone which product practically has all of low dielectriccharacteristics, flame retardancy and heat resistance.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel cyanateester compound capable of giving a cured product not only havingexcellent flame retardancy but also having a low dielectric constant, alow dielectric loss tangent and high heat resistance, a curable resincomposition containing the above compound and a cured product obtainedby curing the above resin composition.

The present inventors have made diligent studies and as a result foundthat a cyanate ester compound represented by the formula (1), preferablycompounds represented by the formulae (2)-(4), more preferably compoundsrepresented by the formulae (5)-(7), gives a cured product which isexcellent in flame resistance and has a low dielectric constant, a lowdielectric loss tangent and high heat resistance. Accordingly, thepresent inventors have completed the present invention.

The present invention provides a cyanate ester compound represented bythe formula (1), preferably a cyanate ester compound represented by anyone of the formulae (2) to (4), more preferably a compound representedby any one of the formulae (5) to (7),

-   -   wherein Ar₂ represents a phenylene group, a naphthylene group or        a biphenylene group, Ar₁ represents a naphthylene group or a        biphenylene group when Ar₂ is a phenylene group, or Ar₁        represents a phenylene group, a naphthylene group or a        biphenylene group when Ar₂ is a naphthylene group or a        biphenylene group, R_(x) represents all substituents of Ar₁,        each R_(x) is the same or different and represents hydrogen, an        alkyl group or an aryl group, R_(y) represents all substituents        of Ar₂, each R_(y) is the same or different and represents        hydrogen, an alkyl group or an aryl group, and n is an integer        of 1 to 50,    -   wherein R₁ to R₄ are the same or different and represent        hydrogen or an alkyl group, n is an integer of 1 to 50, and the        position of each substituent of aromatic rings can be        arbitrarily selected,    -   wherein R₁ to R₄ are the same or different and represent        hydrogen or an alkyl group, n is an integer of 1 to 50, and the        position of each substituent of aromatic rings can be        arbitrarily selected,    -   wherein R₁ and R₂ are the same or different and represent        hydrogen or an alkyl group, n is an integer of 1 to 50, and the        position of each substituent of aromatic rings can be        arbitrarily selected,    -   wherein n is an integer of 1 to 50,    -   wherein n is an integer of 1 to 50.

The present invention further provides a curable resin compositioncontaining the above cyanate ester compound represented by the formula(1), preferably a curable resin composition containing the cyanate estercompound represented by anyone of the formulae (2) to (4), morepreferably a curable resin composition containing the cyanate estercompound represented by any one of the formulae (5) to (7), and a curedproduct obtained by curing the above resin composition.

EFFECT OF THE INVENTION

The cyanate ester of the present invention is capable of giving a curedproduct excellent in flame retardancy and has a low dielectric constant,a low dielectric loss tangent and a high glass transition temperature.For this reason, it is remarkably useful as a high function polymermaterial and can be used as a thermally and electrically excellentmaterial for wide applications such as an electrical insulatingmaterial, an adhesive, a laminating material, a resist and a builduplaminate material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be explained in detail hereinafter. In thecyanate ester compound represented by the formula (1), Ar₂ represents aphenylene group, a naphthylene group or a biphenylene group, and Ar₁represents a naphthylene group or a biphenylene group when Ar₂ is aphenylene group or Ar₁ represents a phenylene group, a naphthylene groupor a biphenylene group when Ar₂ is a naphthylene group or a biphenylenegroup. Specific examples of Ar₁ and Ar₂ include 1,4-phenylene group,1,3-phenylene group, 4,4′-biphenylene group, 2,4′-biphenylene group,2,2′-biphenylene group, 2,3′-biphenylene group, 3,3′-biphenylene group,3,4′-biphenylene group, 2,6-naphthylene group, 1,5-naphthylene group,1,6-naphthylene group, 1,8-naphthylene group, 1,3-naphthylene group and1,4-naphthylene group.

In the cyanate ester compound represented by the formula (1), R_(x)represents all substituents of Ar₁ and each R_(x) is the same ordifferent and represents hydrogen, an alkyl group or an aryl group.Specific examples of R_(x) include a methyl group, an ethyl group, anisopropyl group, a n-butyl group, an i-butyl group, a tert-butyl groupand an isomer pentyl group as the alkyl group and a phenyl group, analkyl phenyl group, a naphthyl group, an alkyl naphthyl group, abiphenyl group and an alkyl biphenyl group as the aryl group.

In the cyanate ester compound represented by the formula (1), R_(y)represents all substituents of Ar₂ and each R_(y) is the same ordifferent and represents hydrogen, an alkyl group or an aryl group.Specific examples of R_(y) include a methyl group, an ethyl group, anisopropyl group, an n-butyl group, an i-butyl group, a tert-butyl groupand an isomer pentyl group as the alkyl group and a phenyl group, analkyl phenyl group, a naphthyl group, an alkyl naphthyl group, abiphenyl group and an alkyl biphenyl group as the aryl group.

In the cyanate ester compound represented by the formula (1), n is aninteger of from 1 to 50.

The cyanate ester compound represented by the formula (1) is preferablya cyanate ester compound represented by any one of the formulae (2) to(4), more preferably a cyanate ester compound represented by any one ofthe formulae (5) to (7). In the cyanate ester compound represented bythe formula (2), R₁ to R₄ are the same or different and representhydrogen or an alkyl group, preferably an alkyl group having 1 to 4carbon atoms, n is an integer of 1 to 50, and the position of eachsubstituent of aromatic rings can be arbitrarily selected.

In the cyanate ester compound represented by the formula (3), R₁ to R₄are the same or different and represent hydrogen or an alkyl group,preferably an alkyl group having 1 to 4 carbon atoms, n is an integer of1 to 50, and the position of each substituent of aromatic rings can bearbitrarily selected.

In the cyanate ester compound represented by the formula (4), R₁ and R₂are the same or different and represent hydrogen or an alkyl group,preferably an alkyl group having 1 to 4 carbon atoms, n is an integer of1 to 50, and the position of each substituent of aromatic rings can bearbitrarily selected.

The process for the production of the compound of the formula (1),including the compounds of the formulae (2) to (7), is not speciallylimited and may be selected from all processes which are present as acyanate synthesis.

For example, IAN HAMERTON, “Chemistry and Technology of Cyanate EsterResins”, BLACKIE ACADEMIC & PROFESSIONAL, discloses a synthesis processfor general cyanate ester compounds. U.S. Pat. No. 3,553,244 provides amethod in which a reaction is carried out in a solvent in the presenceof a base such that cyanogen halide is always present in an excessiveamount based on the base. JP-A-7-53497 discloses a method in which asynthesis is carried out with using a tertiary amine as a base in anexcessive amount based on cyanogen chloride. Japanese Kohyo No.2000-501138 discloses a method which carries out a reaction betweentrialkylamine and cyanogen halide according to a continuous plug flowmethod. Japanese Kohyo No. 2001-504835 discloses a method in whichtert-ammonium halide, which is a by-product obtained in a reactionbetween phenol and a cyanogen halide in a nonaqueous solution in thepresence of a tert-amine, is treated with a cation and anionexchange-couple. Further, Japanese Patent No. 2991054 discloses a methodin which a tertiary amine and cyanogen halide are concurrently added toa phenol compound in the presence of a solvent separable from water toallow them to react, washing with water and liquid separation arecarried out, and purification by precipitation from the thus-obtainedsolution is carried out by using a poor solvent such as a secondary ortertiary alcohol or a hydrocarbon.

The compound of the formula (1) can be obtained by reacting a phenolcompound represented by the formula (8) with cyanogen chloride in asolvent in the presence of a basic compound. Further, there can beadopted a synthesis method in which a salt of the phenol compound of theformula (8) and a basic compound is formed in a solution containingwater and then the salt is reacted with cyanogen chloride by a two-phaseinterface reaction to synthesize the compound of the formula (1).

-   -   wherein Ar₁, Ar₂, R_(x), R_(y) and n are as defined in the        formula (1).

As a general synthesis procedure of cyanate ester, the phenol compoundof the formula (8) is dissolved in an organic solvent, a basic compoundsuch as a tertiary amine is added and then the resultant mixture isreacted with an excessive amount of a cyanogen halide. In this system,since the cyanogen halide is always present in an excessive amount, itis said to be possible to inhibit imidocarbonate, which is to begenerated by a reaction between phenolate anion and cyanate ester.However, since the excessive cyanogen halide reacts with the tertiaryamine to generate dialkylcyanamide, it is necessary to keep the reactiontemperature at 10° C. or less, preferably 0° C. or less, more preferably−10° C. or less.

Other than the above method, the order of addition in the reaction,etc., may be arbitrarily selected. For example, after the phenolcompound is dissolved in solvent, a basic compound such as a tertiaryamine and cyanogen halide or its solution may be alternately dropwiseadded or may be currently supplied. Further, a mixture solution of thephenol compound and a basic compound such as a tertiary amine andcyanogen halide or its solution may be concurrently supplied. In eachcase, the reaction is a large exothermic reaction, while it is necessaryto keep the reaction temperature at 10° C. or less, preferably 0° C. orless, more preferably −10° C. or less, for the purpose of inhibiting aside reaction, etc.

The reaction may be carried out in any form. It may be a batch reaction,a semibatch reaction or a continuous flow reaction.

The basic compound such as a tertiary amine and the cyanogen halide areadded in a total amount of 0.1 to 8 mole, preferably 1 to 3 mol, per 1.0mol of a phenolic hydroxyl group of the phenol compound. In particular,when the phenol compound has a substituent having a steric hindrance atthe ortho position of hydroxyl group, the total amount of the basiccompound such as a tertiary amine and the cyanogen halide needed isincreased as compared with a case where such a substituent is notpresent.

The cyanogen halide to be used is typically cyanogen chloride, cyanogenbromide, etc.

In the phenol compound represented by the formula (8), as the phenolcompound to be used, Ar₂ represents a phenylene group, a naphthylenegroup or a biphenylene group, and Ar₁ represents a naphthylene group ora biphenylene group when Ar₂ is a phenylene group, or Ar₁ represents aphenylene group, a naphthylene group or a biphenylene group when Ar₂ isa naphthylene group or a biphenylene group. Specific examples of Ar₁ andAr₂ include 1,4-phenylene group, 1,3-phenylene group, 4,4′-biphenylenegroup, 2,4′-biphenylene group, 2,2′-biphenylene group, 2,3′-biphenylenegroup, 3,3′-biphenylene group, 3,4′-biphenylene group, 2,6-naphthylenegroup, 1,5-naphthylene group, 1,6-naphthylene group, 1,8-naphthylenegroup, 1,3-naphthylene group and 1,4-naphthylene group. R_(x) representsall substituents of Ar₁, and each R_(x) is the same or different andrepresents hydrogen, an alkyl group or an aryl group. Specific examplesof R_(x) include a methyl group, an ethyl group, an isopropyl group, an-butyl group, an i-butyl group, a tert-butyl group and an isomer pentylgroup as the alkyl group and a phenyl group, an alkyl phenyl group, anaphthyl group, an alkyl naphthyl group, a biphenyl group and an alkylbiphenyl group as the aryl group. R_(y) represents all substituents ofAr₂, and each R_(y) is the same or different and represents hydrogen, analkyl group or an aryl group. Specific examples of R_(y) include amethyl group, an ethyl group, an isopropyl group, an n-butyl group, ani-butyl group, a tert-butyl group and an isomer pentyl group as thealkyl group and a phenyl group, an alkyl phenyl group, a naphthyl group,an alkyl naphthyl group, a biphenyl group and an alkyl biphenyl group asthe aryl group. Further, n is an integer of from 1 to 50.

The compound of the formula (8) can be obtained by, for example, themethods disclosed in Japanese Patent No. 3122834 and Japanese Patent No.2866747. Concretely, there are a method in which a bishalogenomethylcompound such as a compound represented by Ar₂—(CH₂—X)₂ is reacted witha phenol compound in the presence of an acid catalyst or in the absenceof a catalyst, and a method in which a bis(alkoxymethyl) compound suchas Ar₂—(CH₂OR)₂ or a bis(hydroxymethyl) compound such as Ar₂—(CH₂OH)₂ isreacted with a phenol compound in the presence of an acid catalyst.

The basic compound to be used is not specially limited and is selectedfrom organic and inorganic bases. The organic base is preferably anorganic base having a high solubility. Particularly, a tertiary aminewith less side reaction is preferable. The tertiary amine is freelyselected from alkyl amines, aryl amines and cycloalkyl amines. Specificexamples thereof include trimethylamine, triethylamine,methyldiethylamine, tripropylamine, tributylamine, methyldibutylamine,dinonylmethylamine, dimethylstearylamine, dimethylcyclohexylamine,diethylaniline, pyridine and quinoline.

The solvent to be used for the reaction includes ketone solvents such asacetone, methyl ethyl ketone and methyl isobutyl ketone, aromaticsolvents such as benzene, toluene and xylene, ether solvents such asdiethyl ether, dimethylcellosolve, diglyme, tetrahydrofuran,methyltetrahydrofuran, dioxane and tetraethyleneglycoldimethylether,halogenated hydrocarbon solvents such as methylene chloride, chloroform,carbon tetrachloride and chlorobenzene, alcohol solvents such asmethanol, ethanol, isopropanol, methylcellosolve andpropyleneglycolmonomethylether, aprotic polar solvents such asN,N-dimethylformamide, N-methylpyrrolidone, 1,3-dimehtyl-2-imidazolidoneand dimethyl sulfoxide, nitrile solvents such as acetonitrile andbenzonitrile, nitro solvents such as nitromethane and nitrobenzene,ester solvents such as ethyl acetate and ethyl benzoate, hydrocarbonsolvents such as cyclohexane. These solvents may be used alone or incombination in accordance with a reactant.

As a post-treatment after the reaction, generally, a hydrochloric saltof the basic compound such as a tertiary amine, which is a byproduct, isremoved by filtration or washing with water. Taking the washing withwater into consideration, it is preferable to use a solvent which is notmiscible with water in the reaction. Further, there is adopted a methodusing an acidic aqueous solution such as a dilute hydrochloric acid forremoving excess amines in the washing step. For removing a water contentfrom a sufficiently-washed reaction liquid, it is possible to carry outa drying operation by a general method such as sodium sulfate ormagnesium sulfate.

After these operations, a concentration operation, a precipitationoperation or a crystallization operation is carried out. For theconcentration, since the cyanate ester compound has an unstablestructure, a pressure reduction is carried out with keeping 150° C. orlower. For the precipitation or the crystallization, a solvent having alow solubility can be used. For example, an ether solvent, a hydrocarbonsolvent such as hexane or an alcohol solvent may be dropwise added tothe reaction solution. Otherwise, the reaction solution may be inverselydropwise added.

For washing a crude product obtained, there can be adopted a method inwhich a concentrate of the reaction solution or a precipitated crystalis washed with an ether solvent, a hydrocarbon solvent such as hexane oran alcohol solvent. Further, a crystal obtained by concentrating thereaction solution may be again dissolved and then recrystallized.Further, when crystallization is carried out, the reaction solution maybe simply concentrated or cooled. By removing volatile contents from thethus-obtained product according to a method such as drying under reducedpressure, there can be obtained a high-purity cyanate ester compound.

Then, the curable resin composition of the present invention will beexplained. The above curable resin composition is characterized bycontaining the aforementioned cyanate ester compound of the presentinvention. The curable resin composition of the present invention maycontain a cyanate ester compound other than the cyanate ester compoundof the present invention, an epoxy resin, an oxetane resin and/or acompound having a polymerizable unsaturated group.

The cyanate ester compound other than the cyanate ester compound of thepresent invention can be selected from known cyanate ester compounds.Examples of thereof include bisphenol A dicyanate, bisphenol Fdicyanate, bisphenol M dicyanate, bisphenol P dicyanate, bisphenol Edicyanate, phenol novolak type cyanate, cresol novolak type cyanate,dicyclopentadiene novolak type cyanate, tetramethyl bisphenol Fdicyanate and biphenol dicyanate. These cyanate ester compounds may beused alone or in combination.

When the cyanate ester compound is cured, a known curing catalyst may beused. Examples thereof include metal salts such as zinc octylate, zincnaphthenate, cobalt naphthenate, copper naphthenate and acetylacetoneiron, and compounds having an active hydroxyl group such as phenol, analcohol and an amine.

The epoxy resin can be selected from known epoxy resins. Examplesthereof include a bisphenol A type epoxy resin, a bisphenol F type epoxyresin, a biphenyl type epoxy resin, a phenol novolak type epoxy resin, acresol novolak type epoxy resin, a xylene novolak type epoxy resin,triglycidyl isocyanurate, an alicyclic epoxy resin, a dicyclopentadienenovolak type epoxy resin, a biphenyl novolak type epoxy resin, a phenolaralkyl novolak type epoxy resin and a naphthol aralkyl novolak typeepoxy resin. These epoxy resins may be used alone or in combination.

The oxetane resin can be selected from generally known oxetane resins.Examples thereof include alkyl oxetanes such as oxetane,2-methyloxetane, 2,2-dimethyloxetane, 3-methyloxetane and3,3-dimethyloxetane, 3-methyl-3-methoxymethyloxetane,3,3′-di(trifluoromethyl)perfluoxetane, 2-chloromethyloxetane,3,3-bis(chrolomethyl)oxetane, OXT-101 (tradename, supplied by TOAGOSEICo., Ltd.) and OXT-121 (trade name, supplied by TOAGOSEI Co., Ltd.).These oxetane resins may be used alone or in combination.

When the curable resin composition of the present invention contains theepoxy resin and/or the oxetane resin, an epoxy resin curing agent and/oran oxetane resin curing agent may be used. The above epoxy resin curingagent can be selected from generally known epoxy resin curing agents.Examples thereof include imidazole derivatives such as2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole,2-phenyl-4,5-dihydroxymethylimidazole and2-phenyl-4-methyl-5-hydroxymethylimidazole; amine compounds such asdicyandiamide, benzyldimethylamine and 4-methyl-N,N-dimethylbenzylamine;and phosphine compounds such as phosphonium compounds. The oxetane resincuring agent can be selected from known cationic polymerizationinitiators. Commercially available examples include SAN-AID SI-60L,SAN-AID SI-80L, SAN-AID SI-100L (supplied by Sanshin Chemical IndustryCo., Ltd.), CI-2064 (supplied by Nippon Soda Co., Ltd.), IRGACURE261(supplied by Ciba Specialty Chemicals), ADEKAOPTMER SP-170, ADEKAOPTMERSP-150, (supplied by Asahi Denka Kogyo K.K.), and CYRACURE UVI-6990(supplied by Union Carbide Corporation). The cationic polymerizationinitiators can be used as the epoxy resin curing agent. These curingagents may be used alone or in combination.

The compound having a polymerizable unsaturated group can be selectedfrom generally known compounds having a polymerizable unsaturated group.Examples thereof include vinyl compounds such as ethylene, propylene,styrene, divinyl benzene and divinyl biphenyl; (meth)acrylates ofmonohydric and polyhydric alcohols such as methyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,polypropylene glycol di(meth)acrylate, trimethylol propanedi(meth)acrylate, trimethylol propane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate and dipentaerythritol hexa (meth)acrylate;epoxy(meth)acrylates such as a bisphenol A type epoxy(meth)acrylate anda bisphenol F type epoxy (meth)acrylate; a benzocyclobutene resin and a(bis)maleimide resin. These compounds having an unsaturated group may beused alone or in combination.

When the compound having an unsaturated group is used, a knownpolymerization initiator may be used as required. The polymerizationinitiator can be selected from known polymerization initiators. Examplesthereof include peroxides such as benzoyl peroxide, p-chlorobenzoylperoxide, di-t-butylperoxide, diisopropyl peroxycarbonate anddi-2-ethylhexylperoxycarbonate, and azo compounds such asazobisisobutylonitrile.

Further, when the curable resin composition of the present invention isproduced, there may be added a known additive such as a thermoplasticresin, an inorganic filler, a color pigment, an antifoamer, a surfaceconditioner, a flame retardant, an ultraviolet absorber, an antioxidantand a flow regulator, as required. Examples of the inorganic fillerinclude silicas such as natural silica, fused silica and amorphoussilica, white carbon, titanium white, aerosil, alumina, talc, naturalmica, synthetic mica, kaolin, clay, aluminum hydroxide, barium sulfate,E-glass, A-glass, NE-glass, C-glass, L-glass, D-glass, S-glass andM-glass G20. The so-obtained curable resin composition is suitable forvarious applications such as an electrical insulating material, a resinfor a resist, a semiconductor-sealing material, an adhesive for aprinted wiring board, a buildup laminate material, a resin forfiber-reinforced plastics, a sealing resin for a liquid crystal displaypanel, a resin for a color filter of liquid crystal, a coatingcomposition, various coating agents and an adhesive.

The cured product of the present invention can be obtained by curing thecurable resin composition of the present invention, obtained by theabove process, under heat. When the curing temperature is too low, thecurable resin composition does not undergo curing. When it is too high,the cured product deteriorates. Therefore, the curing temperature ispreferably in the range of from 150° C. to 300° C.

The present invention will be explained more concretely with referenceto Examples hereinafter, while the present invention shall not bespecially limited to these Examples.

EXAMPLES Example A1 Synthesis of Cyanate Ester of Biphenyl Novolak(Formula (9): to be Referred to as “G65C”)

Biphenyl novolak having 1.1 mol of OH groups (supplied by Nippon KayakuCo., Ltd., KAYAHARD-GPHG65) and 1.6 mol of triethylamine were dissolvedin 900 ml of 3-methyltetrahydrofuran, to obtain a solution 1. Thesolution 1 was dropwise added to 2,500 g of a methylene chloridesolution of 2.2 mol of cyanogen chloride at −10° C. over 1.5 hours. Themixture was stirred for 30 minutes. Then, a mixed solution of 0.4 mol oftriethylamine and 100 g of methylene chloride was dropwise added, andthe resultant mixture was further stirred for 30 minutes to complete thereaction. A hydrochloride of triethylamine was separated by filtration.The thus-obtained filtrate was washed with 1,000 ml of 0.1 Nhydrochloric acid, and then washing with 1,000 ml of water was repeatedfour times. After drying with sodium sulfate, evaporation was carriedout at 75° C., to obtain a crystal of a yellow solid. The crystal waswashed with diethyl ether and hexane and then dried under a reducedpressure, to obtain a cyanate ester G65C of biphenyl novolak.Identification was carried out by an infrared absorption spectrummeasurement.

Example B1-1 Production of Cured Product

The cyanate ester G65C of biphenyl novolak obtained in Example 1 in anamount shown in Table 1 was added in a short-neck flask. The cyanateester G65C was molten under heat at 150° C. and degassed with a vacuumpump. Then, zinc octylate was added and the resultant mixture wasstirred for 1 minute. The stirred mixture was casted in a mold composedof a glass plate (120 mm×120 mm×5 mmt), a polyimide film (Kapton 200H:DU PONT-TORAY CO., LTD.) and an O-ring made of fluoro rubber (S-100:MORISEI Co., Ltd.), and it was cured by heating in an oven at 170° C.for 1 hour and at 230° C. for 9 hours. After cooling, the polyimide filmwas removed by polishing to obtain a cured product of cyanate estercompound.

The obtained cured product was evaluated for properties by the followingmethods.

Glass transition temperature (Tg): Obtained according to a dynamicviscoelasticity measurement (DMA). The measurement was carried out at anoscillation frequency of 10 GHz.

Dielectric constant and dielectric loss tangent: Obtained according to acavity resonant oscillation method.

Flame resistance: Aflame resistance test was carried out according toUL94. The size of a sample was 10 mm×70 mm×1.5 mm.

Table 1 shows the evaluation results of physical properties.

Example B1-2

A cured product was obtained in the same manner as in Example B1-1except that 50 parts by weight of the G65C obtained in Example 1 and 50parts by weight of bisphenol A dicyanate Skylex, supplied by MitsubishiGas Chemical Company, Inc., were used.

Table 1 shows the evaluation results of physical properties of the curedproduct.

Comparative Example B1

A cured product was obtained in the same manner as in Example B1-1except that the G65C was replaced with bisphenol A dicyanate Skylex,supplied by Mitsubishi Gas Chemical Company, Inc., alone.

Table 1 shows the evaluation results of physical properties of the curedproduct.

Comparative Example B2

A cured product was obtained in the same manner as in Example B1-1except that the G65C was replaced with phenol novolak cyanate PT 30supplied by LONZA.

Table 1 shows the evaluation results of physical properties of the curedproduct. TABLE 1 Example Example Comparative Comparative B1-1 B1-2Example B1 Example B2 Mixing G65C 100 50 — — amount Bisphenol A — 50 100— (Part by dicyanate weight) Phenol — — — 100 novolak cyanate Zincoctylate 0.05 0.05 0.05 0.05 Properties Tg (° C.: DMA) 259 283 304 286Dielectric constant 2.79 2.76 2.73 3.02 (10 GHz) Dielectric loss tangent0.005 0.007 0.011 0.015 (10 GHz) Flame resistance (UL94) V-0 V-1Entirely Entirely burned burned

Example A2 Synthesis of Cyanate Ester of Biphenyl Novolak Monomer(Formula (10): to be Referred to as “BPN-CN”)

A biphenyl novolak monomer having 0.4 mol of OH groups and 0.4 mol oftriethylamine were dissolved in 600 ml of 3-methyltetrahydrofuran, toobtain a solution 1. The solution 1 was dropwise added to a mixedsolution of 220 g of a methylene chloride solution of 0.8 mol ofcyanogen chloride and 400 g of 3-methyltetrahydrofuran at −10° C. over1.5 hours. The mixture was stirred for 30 minutes. Then, a mixedsolution of 0.32 mol of triethylamine and 80 g of3-methyltetrahydrofuran was dropwise added, and the resultant mixturewas further stirred for 30 minutes to complete the reaction. Ahydrochloride of triethylamine was separated by filtration. Thethus-obtained filtrate was washed with 1,000 ml of 0.1 N hydrochloricacid, and then washing with 1,000 ml of water was repeated four times.After drying with sodium sulfate, evaporation was carried out at 75° C.,to obtain a crystal of a yellow solid. The crystal was washed withdiethyl ether and hexane and then dried under a reduced pressure, toobtain a cyanate ester BPN-CN of biphenyl novolak monomer.Identification was carried out by an infrared absorption spectrummeasurement.

Example A3 2,6-bis(4-cyanate-3,5-dimethylphenylmethyl) naphthalene(Formula (11): to be Referred to as “26XNDC”)

0.4 mol of 2,6-bis(4-phenoxy-3,5-dimethylphenylmethyl)naphthalene and1.3 mol of triethylamine were dissolved in 600 ml of3-methyltetrahydrofuran, to obtain a solution 1. The solution 1 wasdropwise added to a mixed liquid of 2,500 g of a methylene chloridesolution of 2 mol of cyanogen chloride and 1,000 g of chloroform at −10°C. over 1.5 hours. The mixture was stirred for 30 minutes. Then, a mixedsolution of 0.6 mol of triethylamine and 100 g of methylene chloride wasdropwise added, and the resultant mixture was further stirred for 30minutes to complete the reaction. The reaction liquid was filtered.Then, the thus-obtained filtrate was washed with 1,000 ml of 0.1 Nhydrochloric acid, and then washing with 1,000 ml of water was repeatedfour times. After drying with sodium sulfate, a concentration operationwas carried out at 75° C. As the concentration operation advanced, awhite crystal precipitated. The white crystal was washed with diethylether and hexane and then dried under a reduced pressure, to obtain awhite crystal, 2,6-bis(4-cyanate-3,5-dimethylphenylmethyl)naphthalene(26XNDC). Identification was carried out by an infrared absorptionspectrum measurement.

Example A4 Synthesis of Cyanate Ester of Naphthol Aralkyl (Formula (12):to be Referred to as “SN485CN”)

Naphthol aralkyl having 0.47 mol of OH groups (supplied by Nippon SteelChemical Co., Ltd., SN485N) and 0.7 mol of triethylamine were dissolvedin 500 ml of chloroform, to obtain a solution 1. The solution 1 wasdropwise added to 300 g of a chloroform solution of 0.93 mol of cyanogenchloride at −10° C. over 1.5 hours. The mixture was stirred for 30minutes. Then, a mixed solution of 0.1 mol of triethylamine and 30 g ofchloroform was dropwise added, and the resultant mixture was furtherstirred for 30 minutes to complete the reaction. The thus-obtainedreaction liquid was washed with 500 ml of 0.1 N hydrochloric acid, andthen washing with 500 ml of water was repeated four times. After dryingwith sodium sulfate, evaporation was carried out at 75° C., to obtain abrown solid. The solid was washed with diethyl ether and hexane and thendried under a reduced pressure, to obtain a cyanate ester of naphtholaralkyl. Identification was carried out by an infrared absorptionspectrum measurement.

Example B2

A cured product was obtained in the same manner as in Example B1-1except that the G65C was replaced with BPN-CN obtained in Example A2.

Table 2 shows the evaluation results of physical properties of the curedproduct.

Example B3

A cured product was obtained in the same manner as in Example B1-1except that the G65C was replaced with a mixture of 50 parts by weightof 26XNDC obtained in Example A3 and 50 parts by weight of bisphenol Adicyanate Skylex, supplied by Mitsubishi Gas Chemical Company, Inc.

Table 2 shows the evaluation results of physical properties of the curedproduct.

Example B4

A cured product was obtained in the same manner as in Example B1-1except that the G65C was replaced with SN485CN obtained in Example A4.

Table 2 shows the evaluation results of physical properties of the curedproduct. TABLE 2 Example B2 Example B3 Example B4 Mixing BPN-CN 100 — —amount 26XNDC — 50 — (Part by SN485CN — — 100 weight) Bisphenol A — 50 —dicyanate Zinc octylate 0.05 0.05 0.05 Properties Tg (° C.: DMA) 231 276274 Dielectric 2.77 2.7 2.86 constant (10 GHz) Dielectric 0.004 0.0070.004 loss tangent (10 GHz) Flame V-0 V-0 V-0 resistance (UL94)

1. A cyanate ester compound represented by the formula (1),

wherein Ar₂ represents a phenylene group, a naphthylene group or abiphenylene group, Ar₁ represents a naphthylene group or a biphenylenegroup when Ar₂ is a phenylene group, or Ar₁ represents a phenylenegroup, a naphthylene group or a biphenylene group when Ar₂ is anaphthylene group or a biphenylene group, R_(x) represents allsubstituents of Ar₁, each R_(x) is the same or different and representshydrogen, an alkyl group or an aryl group, R_(y) represents allsubstituents of Ar₂, each R_(y) is the same or different and representshydrogen, an alkyl group or an aryl group, and n is an integer of 1 to50.
 2. A cyanate ester compound according to claim 1, wherein thecompound of the formula (1) is a compound of the formula (2),

wherein R₁ to R₄ are the same or different and represent hydrogen or analkyl group, n is an integer of 1 to 50, and the position of eachsubstituent of aromatic rings can be arbitrarily selected.
 3. A cyanateester compound according to claim 1, wherein the compound of the formula(1) is a compound of the formula (3),

wherein R₁ to R₄ are the same or different and represent hydrogen or analkyl group, n is an integer of 1 to 50, and the position of eachsubstituent of aromatic rings can be arbitrarily selected.
 4. A cyanateester compound according to claim 1, wherein the compound of the formula(1) is a compound of the formula (4),

wherein R₁ and R₂ are the same or different and represent hydrogen or analkyl group, n is an integer of 1 to 50, and the position of eachsubstituent of aromatic rings can be arbitrarily selected.
 5. A cyanateester compound according to claim 2, wherein the compound of the formula(2) is a compound of the formula (5),

wherein n is an integer of 1 to
 50. 6. A cyanate ester compoundaccording to claim 3, wherein the compound of the formula (3) is acompound of the formula (6).


7. A cyanate ester compound according to claim 4, wherein the compoundof the formula (4) is a compound of the formula (7),

wherein n is an integer of 1 to
 50. 8. A thermosetting resin compositioncontaining the cyanate ester compound recited in claim 1 and a curingagent.
 9. A cured product obtained by curing the thermosetting resincomposition recited in claim 8.